I cant compare the 2500 to these two, as I dont have one. But I have been a Garrett-ite for some time and I can talk about the 1350 and 250. I DO know the 2500 is a good bit heavier than either of these two.
The 1350 is what some have called the "GTI Lite". It doesnt have Image sizing, but offers profiling - a close approximation of size on coin sized targets. A nice thing about this is it uses standard Garrett coils, as it is time based. The GTI series uses special coils with a spearate 3rd winding to effect the Imaging feature. I find the profiiling a nice feature under most coin hunting conditions.
The 1350 is what you might say an extension of the 250, or if you prefer, the ACE is a stripped version of the 1350. They share just about all the same features, but the 1350 is expanded. It has a greater adjustability to each feature and a few other features the 250 lacks, like a SALT mode for instance.
The 1350 is, in every sense, more "active" than the 250. THe processing is more active, the ground balance is "active"
(AutoTracking) the features are more interactive.
The one thing the 250 does better is swing easy. Its lighter and balances differently and you can really get carried away with it if your not careful. There wont be any of that with the 1350 and it can become an armload after a while - I cant imagine how the 2500 fares in this regard!